There has been a problem in that, when a woven or knitted fabric of synthetic fiber or natural fiber is applied to a clothing wherein sweat may be produced during the use, such as sportswear or underwear, an uncomfortable feeling occurs due to the dampness, and the inferior air-permeability, by caused by the sweat.
An air-permeability self-adjustment type woven or knitted fabric has been proposed, as means for eliminating such a uncomfortable feeling caused by sweating, in which the air-permeability of the woven or knitted fabric increases as the humidity within the clothing becomes higher due to sweating, so that moisture dwelling in the clothing is effectively discharged therefrom, while the air-permeability of the woven or knitted fabric decreases as the humidity within the clothing becomes lower when the sweating stops, so that the chilliness due to the excessive discharge of moisture is restricted, whereby the wearing comfort is always maintained.
For example, in Japanese Unexamined Patent Publication (Kokai) No. 3-213518, a woven or knitted fabric including side-by-side type conjugated fibers is disclosed, in which different kinds of polymer layers, namely a polyester layer and a polyamide layer, are bonded together. The wetness of clothing and the deterioration of the air-permeability are eliminated by the deformation of the fiber when moisture is highly absorbed therein by using the difference in moisture absorption between the different kinds of polymer layers. However, in the side-by-side type conjugated fiber, an amount of deformation in fiber configuration is small even if a large amount of moisture is absorbed, whereby the performance thereof has not been sufficiently exhibited. Further, there is another problem in that special production facilities are necessary for simultaneously spinning the two kinds of polymers, resulting in increase in the production cost.
Also, Japanese Unexamined Patent Publication No. 10-77544 discloses a woven or knitted fabric formed of a moisture-absorbing twisted yarn produced by twisting a yarn of moisture-absorbing polymer fibers. This fabric changes its shape from a planar structure to a three-dimensional structure by generating a twisting torque when absorbing moisture to increase the air-permeability. However, this woven or knitted fabric is problematic in that the fabric dimension is becomes unstable because the fabric largely changes from the planar structure to the three-dimensional structure when absorbing moisture. In addition, as a yarn twisting process is necessary, there is a problem in that the production cost rises.